Molecular sieves are classified by the Structure Commission of the International Zeolite Association according to the rules of the IUPAC Commission on Zeolite Nomenclature. According to this classification, framework type zeolites and other crystalline microporous molecular sieves, for which a structure has been established, are assigned a three letter code and are described in the “Atlas of Zeolite Framework Types,” Sixth Revised Edition, Elsevier, 2007.
One known molecular sieve for which a structure has been established is the material designated as LEV, which is a molecular sieve characterized by heptadecahedral cavities to which LEV framework type materials owe their large micropore volume (about 0.3 cm3/g), although this structure only has small eight-membered ring (8MR) pore openings. Due to its unique structure, LEV framework type zeolites are of significant interest as catalysts for methanol-to-olefins (MTO) conversion and NO reduction. Examples of LEV framework type materials include levyne, AIPO-35, CoDAF-4, LZ-132, NU-3, RUB-1, SAPO-35, ZK-20, and ZnAPO-35.
Synthetic LEV framework zeolites are typically prepared using exotic organotemplates as structure directing agents, such as quinuclidine-based templates. The commercial development of LEV framework type zeolites has been hindered by the complexity of the structure directing agent required for its synthesis and hence there is significant interest in finding alternative structure directing agents for the synthesis of aluminosilicate LEV framework type zeolites, particularly materials with SiO2/Al2O3 mole ratios that are suitable for MTO conversion and NO, reduction applications.
It has now been found that LEV framework type zeolites having SiO2/Al2O3 mole ratios ranging from 10 to 55 can be prepared using N,N′-dimethyl-1,4-diazabicyclo[2.2.2]octane dications as a structure directing agent. This cationic species can be produced conveniently and inexpensively from commercially available raw materials.